2. International Relations 1900–1945: World Wars, Economic Collapse, and the Shift in Global Power

Introduction to the World Crisis ($1900-1945$)

This era represents one of the most turbulent and destructive periods in human history, stretching from $1900$ to $1945$. Within this span of $45$ years, the world witnessed two massive world wars, the collapse of four major empires, and a global economic breakdown. The period is marked by extreme brutality, specifically the Holocaust and the introduction of atomic weaponry. The fundamental shift during these decades was the transition of global power from Europe, led by Britain, to the emergence of two new superpowers: the United States and the Soviet Union. This shift raises critical questions for historians and international relations theorists regarding whether this was a time of "deglobalization," where the world became less connected, or if the forces of globalization continued to operate beneath the surface of the surrounding chaos.

The "Real" Twentieth Century and the Advent of Total War

Historian Eric Hobsbawm famously proposed that the "real" $20$th century did not begin in $1900$ but in $1914$. This year marked the end of a relative century of peace maintained by European states since the Napoleonic Wars. The conflict that began in $1914$, World War One, was the first truly global war and the first instance of Total War. Total War means a war in which a country uses all its resources — soldiers, factory workers, women, industry, and propaganda — to defeat the enemy. This concept is vital because it blurs the line between military and civilian life, effectively turning entire societies into war machines. The death tolls from this era are staggering, including the Nazi genocide of $6 \times 10^6$ Jews and the atomic bombings of Hiroshima and Nagasaki, signaling a fundamental collapse of civilized norms.

Germany’s Rise and the Erosion of the Balance of Power

A primary cause of the shift in world politics was Europe losing its dominant position. By $1945$, much of the continent was in ruins, and Eastern Europe was occupied by the Soviet Union. Some historians describe the two world wars as a single "Thirty-Year War" that originated with the unification of Germany in the $1870s$. Before $1871$, Germany was a collection of $25$ separate states; Prussian Chancellor Otto von Bismarck unified them through three wars, creating a massive new power in Central Europe. Germany industrialized with incredible speed, surpassing Britain in the production of coal, iron, and steel by $1914$. German leaders sought "a place in the sun," looking for overseas colonies and markets. This ambition disrupted the balance of power, which is the idea that no single country should become so strong it can dominate all others — other states form alliances to keep the strongest power in check. This principle was the core organizing force of European international relations.

Imperial Rivalry, the Alliance System, and the "Eastern Question"

German expansionism brought it into direct competition with Britain and France, who already controlled large portions of Africa, Asia, and the Middle East. To counter Germany, an alliance formed between Britain, France, and Tsarist Russia, while Germany allied with Austria-Hungary. Many Germans viewed the existing imperial system as rigged against them. Simultaneously, the slow collapse of the Ottoman Empire (the "Eastern Question") created a power vacuum in the Balkans. Nationalism, defined as the belief that people sharing a common culture, language, or ethnicity should govern themselves in their own state, became a key trigger for conflict. When a Serbian nationalist assassinated Austro-Hungarian Archduke Franz Ferdinand in June $1914$, the complicated alliance system dragged the continent into war. Historians like Fritz Fischer in his book Bid for World Power ($1961$) argue Germany deliberately planned the war for European domination, while others point to the Schlieffen Plan. The Schlieffen Plan was Germany's military strategy for fighting a two-front war — knock France out quickly in the west, then turn east to fight Russia; this strategy meant a regional conflict with Russia automatically escalated into a world war involving France.

Peacemaking and the Treaty of Versailles ($1919$)

At the end of World War One, peacemakers at Versailles faced a world in chaos with millions dead, collapsed empires, and the Bolshevik Revolution in Russia. A major issue was reparations, which are payments a defeated country must make to the winners to help cover the costs of the war. Germany’s massive reparations bill caused economic hardship and political resentment later exploited by Hitler. US President Woodrow Wilson introduced his Fourteen Points, advocating for open diplomacy, free trade, and the League of Nations based on collective security. Collective security means that a group of countries agrees to defend any one of its members if it is attacked — the idea that "an attack on one is an attack on all." While $60 \times 10^6$ people gained their own states through national self-determination, approximately $25 \times 10^6$ were left as minorities in states that did not represent them. Furthermore, self-determination was denied to colonized peoples in Asia and Africa, whose lands became League Mandates. The treaty stripped Germany of $13\,\%$ of its territory and included a "war guilt" clause. John Maynard Keynes warned this would ruin the European economy, and General Foch predicted Versailles was only "an armistice for twenty years."

The Great Depression and the Rise of Extremism

By the early $1900s$, the US began replacing Britain as the global economic center. By $1929$, the US generated an extraordinary $42\,\%$ of the world’s industrial output, whereas Britain, France, and Germany combined accounted for only $28\,\%$. On October $29$, $1929$, the Wall Street Crash occurred, leading to the Great Depression. The Great Depression was a worldwide economic collapse that began after the $1929$ stock market crash and lasted through most of the $1930s$. It resulted in mass unemployment, the drying up of US loans, and worthless currencies. In the Global South, demand for raw materials vanished; for example, coffee farmers in Brazil burned their crops as railway fuel. This suffering allowed extremist movements to thrive, leading to Hitler's victory in $1933$, Mussolini's fascist takeover in Italy, and Franco's victory in Spain. Many states retreated from global trade toward autarky, which means a country trying to be economically self-sufficient — not relying on imports or international trade.

Interwar Superpowers and Japanese Expansionism

The USSR, following the $1917$ Bolshevik Revolution and a civil war between $1918$ and $1920$, remained largely inward-looking under Stalin's "socialism in one country." Meanwhile, the US pursued isolationism, which is a foreign policy of avoiding involvement in other countries' conflicts and alliances. Although the US never joined the League of Nations, it remained an economic powerhouse, providing loans that created a circular financial flow between Germany, the Allies, and the US. In the East, Japan underwent the Meiji Restoration (starting in $1868$), which refers to the period when Japan modernized rapidly, abolishing its feudal system and building a Western-style industrial economy and military. Japan felt cheated by the Versailles settlement and sought a "co-prosperity sphere" in Asia. In $1931$, Japan occupied Manchuria and created a puppet state called Manchukuo. A puppet state is a country that appears independent but is actually controlled by a foreign power. The League's failure to react to the Manchurian Crisis emboldened other dictators. Tensions with the US over Chinese trade led to the Japanese attack on Pearl Harbor on $7$ December $1941$, making the war truly global.

The Path to War in Europe and Fascist Ideology

Historians debate whether World War Two was solely "Hitler's War" or driven by structural forces. A.J.P. Taylor argued Hitler was an opportunist, but most believe he had long-term expansionist goals. Mussolini established Fascism in Italy in $1922$. Fascism is a political system that places the nation and state above all individual rights, glorifies militarism and violence, eliminates political opposition, and is led by a single powerful dictator. Hitler's Nazism added a racial core to this, seeking Lebensraum. Lebensraum means "living space" in German — Hitler's belief that Germany needed to conquer land to the east to provide room and resources for the German people. This ideology led to the invasion of Poland and the Soviet Union, as well as the Holocaust. Britain and France initially responded with appeasement, which means giving in to an aggressor's demands in hopes of avoiding a larger conflict. This policy failed at the Munich Conference in September $1938$, as Hitler soon seized the rest of Czechoslovakia and invaded Poland in September $1939$, triggering the war.

Theories of Global History and the Paradox of Globalization

International relations theories offer different lenses for these events. Realists, such as E.H. Carr in The Twenty Years' Crisis ($1939$), see the period as proof that states pursue power and self-interest. Liberals/Idealists highlight the cross-border cooperation of feminist, worker, and anti-colonial movements, viewing the League as a precursor to the United Nations. World systems theory, discussed by Giovanni Arrighi, views the era as a turbulent transition of global hegemony from Britain to the US, part of a $500$-year process. Although the period saw a retreat into protectionism and autarky (deglobalization), cultural globalization continued through radio, cinema, Hollywood, and jazz. Political ideas like communism and feminism also spread internationally. Between $1891$ and $1920$, $27 \times 10^6$ Europeans emigrated, and by $1920$, $1$ in $7$ US residents was foreign-born. However, this period also involved forced labor and displacement, proving that for many, "the world becoming smaller" was a violent and oppressive experience. The failures of this era directly shaped the post-$1945$ international order, including the UN and global financial systems.